Exhaust question, need input!

[Jim B.]

What's up everyone! I have a question about my 76' eliminator jet that's about to be finished in another month. My question is pertaining to the exhaust system. My motor is a 468 cu in. chevy, 10-71 littlefield, ported merlin 345's, clay smith solid flat tappet(.640 lift) and (276 duration at .050 lift). Going to start with about 8-9 of boost on C-12. Hoping for 800hp. This combo should do it. Anyway, I'm runnin' zoomies and I have a bad feeling that they won't be on for long because of all this noise law bullshit. I've looked at other options, headers with collector mufflers, Banderlog water injection valve, etc. The problem is as most of you know is that I'm runnin' a large camshaft with alot of duration and overlap so I want to stay away from water injected header all together. I've seen guys runnin' offshore type exhaust manifolds that dump over the transom like a header. Can anyone elaborate on this?Can I run my motor this this type of exhaust and will it quite the motor down? I don't much about that type of exhaust, just headers and such. I appreciate any help, opinions, etc. THANKS! Jim:cool:

[77charger]

Maybe a lightning type hearder that is water jacketed.might be what you are looking for

[Heatseeker]

I'm running a similar set up to your's. I'm going to try building some Supertrapps for my headers. You can buy them in pieces and they have some 4" parts available. Hopefully, I can quiet it enough to keep my headers!
I've always run water injection headers(it's required on my "home" lake). It does soften the exhaust noise a touch. If you go that route and use the Banderlog valve, you'll have no reversion problems no matter what cam you're running.

[1Bahnerjet]

Hey Heatseeker,
Where's your "Home Lake" ?

[Rexone]

My experience with Supertrapps is that to get them quiet enough they will be restrictive and use substantial power. Add rings to not lose power, they get too noisy. And, water (which is essential for noise reduction) give a big sprinkler head effect (very messy). Salt water also corrodes the rings up and clogs them up.

[Cs19]

I was just having a conversation about this with one of my fabricator buddies who makes headers.
I was asking him if he knew of a way to come up with something to get our decibals down. Either using something with our current bassetts or maybe make a whole new header,but we obviously need keep the power loss at a minimum and maybe something thats removable for race weekends.He had a few really good ideas..
There are lots of us with over the transom headers, and it sounds like they are already cracking down.Something is gonna have to happen, there is no way we are going to pass with full water and mufflers.Still wayyy to loud.
Any ideas?

[Heatseeker]

Jim B., my home lake is Lake Don Pedro. The sheriff there is usually not too strict, but if you come around the marina with open headers, they'll write you. Same goes for dry headers in open water.
Rexone, thanks for your input on the supertrapps. Salt water will not be a concern in my case. Isn't any effort to quiet headers down going to result in some sort of power loss? Have you heard of or seen anything effective yet? I'm willing to give up a little power to keep my headers!
CS19, what are these ideas your fab buddy came up with? We need to all get together on this, so we can continue to enjoy our hobby to it's fullest!

[Rexone]

Originally posted by Heatseeker
Rexone, thanks for your input on the supertrapps. Salt water will not be a concern in my case. Isn't any effort to quiet headers down going to result in some sort of power loss? Have you heard of or seen anything effective yet? I'm willing to give up a little power to keep my headers!
High alkali content water will also clog supertrapps with deposits.
Isn't any effort to quiet headers down going to result in some sort of power loss? ...
The design & technology exists to meet noise requirements without power loss (we have it now in a new product coming for thru-transom).
The problem with headers is two fold that doesnt exist with thru-transom. 1. Use of substantial water flow to assist sound reduction is undesireable because of reversion and / or backflow down the headers into the exhaust... 2. The cosmetic factor of making a small attractive package that won't make having nice looking headers a memory. Those two factors are the main problems in muffling over transom without power loss as I see it. Killing the noise isn't a problem, we know how to do this. But with present insert type mufflers power loss is a given because of the two factors above. We have tested insert mufflers that are absolutely legal noise wise but are so restrictive they're not even worth considering building from a performance perspective.

[1Bahnerjet]

Heatseeker,
Thanks for the Reply. Been to Don Pedro its nice, the smooth water is at top of Lake (Mocasin sp?) But don't you have Smooth Water right in Lathrop (the River)?

[Jim B.]

Hey Bahner and heatseeker,
I am going to use my boat mostly at the river up around needles and below parker. I have some friends of mine here in El Segundo where I live that go to needles and haven't had a problem with noise yet. Keep in mind, they usually go during the week. I also do go to other various lake in CA and one of them being Lake Don Pedro. My girlfriend loves that place and it's also great Lake to get away and go skiing. Heatseeker your a lucky bastard if that's your home lake!!HA!!HA!! By the way can a lighting header dump over the transom?? the only one's I've seen go through the transom.

[bp]

about a year and a half ago, a guy brought his river hydro out to ming to run the rr class. he had headers with borla mufflers installed on the thing with no water injection. the headers were jet coated, and looked great. these were the same type mufflers you see on supercomp dragsters.
he said his engine made more power with the borlas than with open collectors. all i know is that it was very mellow sounding, and not loud at all.
he said he lived at havasu, and ran the thing up and down the river; the jethot coating was holding up real well, and no one ever hassled him about noise.

[Jim B.]

Hey BP, Thanks for the input. I have indeed checked into those as well and as far as collector mufflers go I think they look the best. I am probably going to have a set of custom headers made with borla collector mufflers and then have them ceramic coated.:D

[Heatseeker]

Originally posted by 1Bahnerjet
Heatseeker,
Thanks for the Reply. Been to Don Pedro its nice, the smooth water is at top of Lake (Mocasin sp?) But don't you have Smooth Water right in Lathrop (the River)?
Yea, the river is literally 5 minutes from my driveway to launch. I like to call it my personal launch! I only go out there on weekdays(weekends are punishment :eek: ), and I'm usually one of only a few boats out.
My cuz has a houseboat on Don Pedro. His dad built their first one in 63. My first trip was in 65, when I was 6 months old! That's why it's my home lake! Whenever one of you plan a trip up, let me know.

[BiggusJimbus]

I think it might be wise to investigate what these guys are doing.
I know some of them have some pretty strict noise requirements, so they have probably a lot of knowledge to share.
http://www.nzjba.org/rulesregs/noise.htm

[Cs19]

drag muffler.
http://www.burnsstainless.com/DragMuffler/a_larry1.jpg
http://www.burnsstainless.com/DragMuffler/a_larry3.jpg
Ultralite stainless steel muffler.
I do not know if either of these will get us to where we need to be decibal wise, but its one of our options.Lots of different sizes ,etc. are available. I will try to get more info later this week.
http://www.burnsstainless.com/UltraliteMuffler/SSmuf-2.gif http://www.burnsstainless.com/UltraliteMuffler/SSmuf-7.gif

[manuel]

I have no explanation for this but here it is, I have a 468" 10:1, cam #'s not known but idles lumpy, had logs with risers and 3"dia. short through transoms with rubber flappers, I switched to Lightning headers with 4" dia. 10" long tips with internal butterflys still coming out at same location , now the weird part, at idle my boat was MUCH LOUDER before the changes ! it's a MUCH deeper real nice sound now and the lope of the cam is more noticiable but it's quieter. at 3,000 to 5,700rpm it's about the same as before, I only went with the longer tips because I have a full width swim platform right above the exits and it was getting exhaust soot on it, where I live they don't bother with noise levels, Manuel